Balancer shafts for use in multicylinder engines

A balancer shaft for use in a mutlicylinder engine, which is sustained by a cylinder block of the engine to be arranged in substantial parallel with a crank shaft in the engine and driven to rotate by the crank shaft, the balancer shaft comprising:

• a balance weight part formed to be eccentric in relation to a rotation axis of the balancer shaft and disposed at a central area in the cylinder block in the direction along the alignment of cylinders,
• an elongated shaft part having one end portion connected with one end portion of said balance weight part and extending therefrom in the direction along the alignment of cylinders with an axis coinciding with the rotation axis of the balancer shaft,
• a driving device provided on the other end portion of said elongated shaft part for transmitting the rotation of the crank shaft to the balancer shaft,
• a first journal provided on the other end portion of said elongated shaft part to be supported to turn by a first bearing portion provided in the engine,
• a second journal provided on a central portion of said balance weight part to be supported to turn by a second bearing portion provided in the engine, and
• a third journal provided on the other end portion of said balance weight part to be supported to turn by a third bearing portion provided in the engine;
• said first journal being supported by the first bearing portion provided in an end wall of the cylinder block in which first to fourth cylinders are arranged in line, said second journal being supported by the second bearing portion provided in a first bulkhead located between the second and third cylinders in the cylinder block, and said third journal being supported by the third bearing portion provided in a second bulkhead adjacent to said first bulkhead in the cylinder block, a first portion of the balancer shaft extending from said second journal to said first journal being longer than a second journal of the balancer shaft extending from said second journal to said third journal, and said third journal is provided with the radius thereof smaller than a maximum distance from the rotation axis of the balancer shaft to an outer surface of said balance weight part.

A balancer shaft for use in a multicylinder engine, which is sustained by a cylinder block of the engine to be arranged in substantial parallel with a crank shaft in the engine and driven to rotate by the crank shaft, which is used as each of a couple of shafts disposed to face each other with the crank shaft between and rotate in the respective directions opposite to each other at speed being twice as high as the speed of rotation of the crank shaft in the cylinder block forming therein four cylinders arranged in line, and which is inserted in the cylinder block through an end wall thereof so as to extend to pass through bulkheads provided in the cylinder block, the balancer shaft comprising:

• a balance weight part formed to be eccentric in relation to a rotation axis of the balancer shaft and disposed at a central area in the cylinder block in the direction along the alignment of cylinders,
• an elongated shaft part having one end portion connected with one end portion of said balance weight part and extending therefrom in the direction along the alignment of cylinders with an axis coinciding with the rotation axis of the balancer shaft,
• a driving device provided on the other end portion of said elongated shaft part for transmitting the rotation of the crank shaft to the balancer shaft,
• a first journal provided on the other end portion of said elongated shaft part to be supported to turn by a first bearing portion provided in the engine,
• a second journal provided on a central portion of said balance weight part to be supported to turn by a second bearing portion provided in the engine, and
• a third journal provided on the other end portion of said balance weight part to be supported to turn by a third bearing portion provided in the engine;
• said first journal being supported by the first bearing portion provided in the end wall of the cylinder block, said driving device including a gear mounted on the other end portion of said elongated shaft part projecting through the end wall to the outside, said second journal being supported by the second bearing portion provided in a first bulkhead located between the second and third cylinders, said third journal being supported by the third bearing portion provided in a second bulkhead located between the third and fourth cylinders and is so formed that at least one of the dimensions of said third journal selected from the group consisting of the length of said third journal along the rotation axis of the balancer shaft and the diameter is smaller than the corresponding dimension of said first journal, and said balance weight part has a first section and a second section, said second section elongating from said journal to said third journal and being slightly shorter than said first section, said first section of the balance weight part being so formed that a maximum distance from the rotation axis of the balancer shaft to an outer surface of said first section is smaller than the diameter of said first journal, and said second section of the balance weight part being so formed that a maximum distance from the rotation axis of the balancer shaft to an outer surface of said second section is smaller than the diameter of said second journal.

A balancer shaft for use in a multicylinder engine, which is sustained by a cylinder block of the engine to be arranged in substantial parallel with a crank shaft in the engine and driven to rotate by the crank shaft, which is used as each of a couple of shafts disposed to face each other with the crank shaft between and rotate in the respective directions opposite to each other at speed being twice as high as the speed of rotation of the crank shaft in the cylinder block forming therein four cylinders arranged in line, and which is inserted in the cylinder block through an end wall thereof so as to extend to pass through bulkheads provided in the cylinder block, the balancer shaft comprising:

• a balance weight part formed to be eccentric in relation to a rotation axis of the balancer shaft and disposed at a central area in the cylinder block in the direction along the alignment of cylinders,
• an elongated shaft part having one end portion connected with one end portion of said balance weight part and extending therefrom in the direction along the alignment of cylinders with an axis coinciding with the rotation axis of the balancer shaft,
• a driving device provided on the other end portion of said elongated shaft part for transmitting the rotation of the crank shaft to the balancer shaft,
• a first journal provided on the other end portion of said elongated shaft part to be supported to turn by a first bearing portion provided in the engine,
• a second journal provided on a central portion of said balance weight part to be supported to turn by a second bearing portion provided in the engine, and
• a third journal provided on the other end portion of said balance weight part to be supported to turn by a third bearing portion provided in the engine;
• said first journal being supported by the first bearing portion provided in the end wall of the cylinder block, said driving device including a gear mounted on the other end portion of said elongated shaft part projecting through the end wall to the outside, said second journal being supported by the second bearing portion provided in a first bulkhead located between the second and thrid cylinders, said third journal being supported by the third bearing portion provided in a second bulkhead located between the third and fourth cylinders and is provided with a diameter smaller than the diameter of said second journal, and said balance weight part having a first section and a second section elongating from said second journal to said third journal and being slightly shorter than said first section, said second section of the balance weight part being so formed that a maximum distance from the rotation axis of the balancer shaft to an outer surface of said second section is larger than the diameter of said third journal but smaller than the diameter of said second journal.